[Billy Gun]

I was recently comparing several amp's specs and noticed the Sunfire units have a 0.5 THD. spec. very high.....Hell, even my My Yamaha receiver has a a THD spec that is 10 times lower than that (.05 THD)


#1 What does the THD spec indicate/what does it mean?


#2 Is it really that important of a spec.?

 

[tubeguy44]

bob carver's philosophy is that 0.5% is lower than people can hear and he rates all his amps at that distortion rating......


but if you look at independent tests of his amps, you will usually see lower distortion numbers.....


here is the summary of one review...
Quote:

I too have been listening with, intense appreciation, this smooth beast of an amplifier. I might go even further than Noel. I find its performance, compared to any amplifier at any price, competitive. There. I said it! I’ve told this to many audiophiles who otherwise couldn’t believe that a Sunfire amplifier designed by Bob Carver can sound soooo damn good. Being a high ticket, best-design-you-can-think-of type guy, no one was more surprised by the sound of this amp than I. Its performance is virtually flawless compared to the Sim Audio W10 Mono’s that retail for about $10,000. I could not for the life of me find what the W10’s did that would be considered significantly better. They certainly don’t sound two and one/half times, or $7,000 better. On the other hand, the KR amplifiers that Noel continues to refer to as world beaters (at $28,500 they'd better be!), would probably blow up (as my units have three times previous) if they were asked to reproduce a fraction of the power coupled with the extreme finesse Carver’s Sunfire produces. This is not to say that the KR’s don’t produce great sound. They do. Even so, I remain dumbfounded by this Sunfire amp. I’m now listening to only 16/44.1 CD’s to see if those SACD’s are part of the reason behind its exceptional performance. The sound is liquid, detailed, fast, taut, and tight in the low end, and as musical as one could possibly hope for anywhere near the Sunfire's price. So what we have, dear reader, is an amplifier that in most setups should simply astound regardless of what amplifier you own. As far as I'm concerned, the Sunfire earns no less than the highest praise.

http://www.stereotimes.com/amp010500.shtm



cheers!

 

[Bondmanp]

For a definition of THD, see http://www.enjoythemusic.com/audioterminology.htm#T


look under distortion and harmonic


THD measurements are controversial. Some believe that below 1.0%, 0.5% or 0.2%, THD becomes inaudible. Some feel that the lower the THD the better, ad infinitum.


Some of the most well-regarded amplifiers, especially tube models, have rather high THD specs. One reason for this is that super-low THD specs require the use of negative feedback in an amplifier, which compares the output signal to the input signal in an effort to reduce distortion by cancelling any differences in the output signal. The use of varying degrees of negative feedback is also controversial. Some feel it sacrifices other sonic qualities, like pace, rythm, timing and transient response, for lower distortion. Many also feel that excessive use of negative feedback can introduce frequency imbalances, and blame this for amplifiers (usually solid state) that are excessively bright in the 4-8kHz band. Some feel that this trade-off is not worth it. Many also feel that Intermodulation Distortion (IM) is much more audible than harmonic distortion, and focus on minimizing IM.


Go with what amp sounds best to you, with your other gear in your room. I believe that ear/system/room synergy ultimately determines what works for every part of the audio chain. YMMV

 

[JorgeLopez11]

One more comment,


Perhaps this is a digital amp, so its THD rating should be higher han the usual analog amps ratings. I think Tubeguy owns one of them, so may be he can explain this in detail.


In any case, THD has little meaning particularly due to the fact most manufacturers do not show the complete THD figures. The THD+Noise spec is much more useful anyway.


Apart from the link provided by Bondmanp, I highly recommend you the white paper at Rane's site ( www.rane.com ) regarding audio measurements specs. The whole subject is covered thoroughly.


Enjoy!

 

[tubeguy44]

the sunfire is not a digital amp.....


it uses a switching power supply of bob carver's design called "Tracking Downconverter power supply".....


the use of this power supply is how he achieves the power ratings he does in such a comparatively light package....


you can read more about it on the attached link....this links to the list of white papers in pdf format...

http://www.sunfire.com/technology.htm


cheers!

 

[Dan Krieg]

Also keep in mind that the .5 spec is the maximum at full output. During normal use, it will be less.

 

[MrMcGoo]

The high THD specification almost convinced me not to buy Sunfire. A member on this board said not to worry about it. I purchased a Sunfire CG II 225x5 and am very happy with it. I was amazed at how much better the Sunfire is in the bass frequencies than my prior amp rated at 140 wpc x2. The Sunfire thrives on low impedance loads.


Bill

 

[Enigma]

The .5% thd spec is just Bob Carver thumbing his nose at "conventional wisdom". No Sunfire amp, receiver, etc has any other spec. He doesn't believe it's audible, so who cares. All tests I have read are much lower; typically around .1 IIRC. I also believe that the 200 w/ch amp and the newer 225 w/ch amp are the same; having a .5% distortion spec allows him to move further up the curve, claim more power for the same product, yet still be factually correct.

 

[Larry Fine]

Quote:

Originally posted by tubeguy44 the sunfire is not a digital amp..... it uses a switching power supply of bob carver's design called "Tracking Downconverter power supply".....

From what I remember of what I've read in the past, the power supply itself is basically a digital amp, whose modulated voltage remains at about 6 volts above the desired output voltage, so only 6 volts is dropped across the output transistors. This is why the amps run cool.

 

[Billy Gun]

ok, so the THD spec sounds insignificant.


But why are so many people complaining about excessive hiss and "Hum" from the Sunfire Vs "Conventionally designed" amps?


Is the hiss and hum coming from the amp not reflected/or related to the high THD spec???


I may be confused......

 

[tubeguy44]

Quote:

Originally posted by Billy Gun ok, so the THD spec sounds insignificant. But why are so many people complaining about excessive hiss and "Hum" from the Sunfire Vs "Conventionally designed" amps? Is the hiss and hum coming from the amp not reflected/or related to the high THD spec??? I may be confused......

i'm not sure where you are reading that..... ask any of the current owners on this thread or in this forum....


i haven't seen any of them post that type of comment..... the couple of sunfires that i auditioned were dead quiet with no signal present and between tracks.....


cheers!

 

[sullyj]

Yep, total silence. I've read alot of amp threads and can't recall that. Read the link tubeguy gave you for the amplifier whitepaper on the technology. If you put 'bob carver' in google you'll find an interview (audio ideas guide, I think) where carver talks some about distortion. Good luck!

 

[JorgeLopez11]

Tubeguy,


I've read a little about this switching mode power supplies. I found the Tripath whitepapers particularly helpful, but the link you provided has very interesting documentation as well.


Thanks!

 

[MrMcGoo]

My Sunfire amp is driving ultra sensitive Klipsch RF-7s rated at 102 db/2.83v/1m. There is a very faint hiss that can only be heard within 6 inches of the tweeter when no program material is playing. I never notice the hiss in routine use, but I do notice the improved dynamics and detail from the Sunfire.


Bill

 

[Larry Fine]

Me too, me too!


I own a Stereo and a Cinema Grand. Powerful, cool, clean, and quiet.

 

[tubeguy44]

see.....


i told ya.....


the owners here agree that the sunfires are very quiet......

 

[Staged]

My sunfire CG II has a louder hiss with no input than my RMX2450, but I cannot hear it at all from my listening position at all. It is basically silent from my seating postition.


I can hear hiss from twice the distance compared to the RMX2450.

Gain is turned up about 1/3 on the RMX.



MY CG sounds great though and could easily run my mains, but in about over blind A/B tests, I either chose the RMX2450 or could not hear a difference.

 

[Billy Gun]

Quote:

Originally posted by tubeguy44 i'm not sure where you are reading that..... ask any of the current owners on this thread or in this forum.... i haven't seen any of them post that type of comment..... the couple of sunfires that i auditioned were dead quiet with no signal present and between tracks..... cheers!

reading it at Audiohlics.audioreview.com


here several examples of the complaints about the Sunfire being noisy:


......btw, I also had that damn buzzing/ground problem. the noise floor was TOO high with this amp. My aragon runs very quiet.


......I am deeply bothered by this very audible hum. I thought it was an isolated problem until I read these reviews.


......When it was on, there was a very obnoxious hum from all five speakers that clearly audible, even over music.


......It hummed rather

loudly. (2) It hummed over ALL the channels through the speakers, much louder

through the center and left rear channels



so whether or not this is related to the high THD spec I have no idea.


This may be related to the Tracking downconverter design.


But with this many complaints about noise there is a trend here worth noting


I am concerned about noise since I am running KLF-30's

 

[tubeguy44]

bill (mrmcgoo) above runs RF-7's with his sunfire...... same sensitivity as your KLF-30's....... (great speakers btw - i love mine!!!)

 

[MrMcGoo]

Any brand name amp can run into a hum problem with ground loops. I do not think that any Sunfire is likely to produce excessive hiss. The Sunfire has both the usual RCA inputs plus balanced inputs to help reduce noise.


Bill